This is a photo of lahar deposits near Santa Maria volcano (Guatemala).
This used to be a wide, deep river valley, and you can see the
far wall of the valley where the trees are growing. The lahar
deposits extend from that far wall to behind where this photo
was taken. You can see that between lahar events the river cuts
into the lahar deposits, but every time there is another event,
it fills up again. The people give an idea of the size of stones
that can be carried by a lahar.

This photo give somewhat of an idea about the distance that lahars
can travel. This photo was taken some 15 km from the base of
Santa maria, and the plain of lahar material has filled the river
valley and spread to a width of almost a kilometer. The truck
that is driving across the deposit gives a sense of the size of
stones that can be carried even this far. In the distance is
Santa Maria volcano. The scar that formed from the big 1902 eruption
is clearly visible because it does not support vegetation. In
this photo Santiaguito dome has just had a small eruption.